Hawzah News Agency – The merciful prophet of Islam (pbuh) says:

إنَّ أطيَبَ الكَسبِ كَسبُ التُّجّارِ الذينَ إذا حَدَّثُوا لم يَكذِبُوا ، وإذا ائتُمِنُوا لم يَخُونُوا ، وإذا وَعَدُوا لم يُخلِفُوا ، وإذا اشتَرَوا لم يَذُمُّوا ، وإذا باعُوا لم يُطرُوا ، وإذا كانَ علَيهِم لم يَمطُلُوا ، وإذا كانَ لَهُم لَم يُعَسِرُوا.

'The best of earnings is the earning of traders who when they speak they do not lie, when they are entrusted with something they do not betray, when they promise they do not breach, when they buy they do not defame [the goods], when they sell they do not praise [their own goods], when they are in debt they do not delay its repayment, and if they are owed [money] they do not force [their debtor].'

Source: Kanz al-Ummal, no. 9340-9341